﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using ylyfDataCommon.Exceptions;

namespace ylyfDataCommon.Cypher
{
    public class AESPrivider:CypherProvider
    {
        public override string Encryption(string str, string KEY = null, string IV = null)
        {
            byte[] Key = Encoding.UTF8.GetBytes(KEY);
            byte[] IVstr = Encoding.UTF8.GetBytes(IV);
            // Check arguments.
            if (str == null || str.Length <= 0)
                throw new ArgumentNullException("plainText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("IV");
            byte[] encrypted;
            // Create an AesCryptoServiceProvider object
            // with the specified key and IV.
            using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
            {
                aesAlg.Key = Key;
                aesAlg.IV = IVstr;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for encryption.
                using (MemoryStream msEncrypt = new MemoryStream())
                {
                    using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    {
                        using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                        {

                            //Write all data to the stream.
                            swEncrypt.Write(str);
                        }
                        encrypted = msEncrypt.ToArray();
                    }
                }
            }


            // Return the encrypted bytes from the memory stream.
            return Convert.ToBase64String(encrypted);
        }

        public override string Decryption(string str, string KEY = null, string IV = null)
        {
            if (string.IsNullOrWhiteSpace(KEY) || string.IsNullOrWhiteSpace(IV))
            {
                throw new DecryptionNotSupportException("解密方法需要提供密钥和偏移量");
            }
            byte[] Key = Encoding.UTF8.GetBytes(KEY);
            byte[] IVstr = Encoding.UTF8.GetBytes(IV);
            byte[] cipherText = Convert.FromBase64String(str);
            // Check arguments.
            if (cipherText == null || cipherText.Length <= 0)
                throw new ArgumentNullException("cipherText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("IV");

            // Declare the string used to hold
            // the decrypted text.
            string plaintext;

            // Create an AesCryptoServiceProvider object
            // with the specified key and IV.
            using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
            {
                aesAlg.Key = Key;
                aesAlg.IV = IVstr;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for decryption.
                using (MemoryStream msDecrypt = new MemoryStream(cipherText))
                {
                    using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        {

                            // Read the decrypted bytes from the decrypting stream
                            // and place them in a string.
                            plaintext = srDecrypt.ReadToEnd();
                        }
                    }
                }

            }

            return plaintext;
        }
    }
}
